1. Field of the Invention
This invention relates to nonaqueous resin dispersions and particularly to polyelectrolyte resin plastisols and organosols. This invention also relates to photosensitive polyelectrolyte resin plastisols and organosols that contain a photopolymerizable ethylenically unsaturated compound.
2. Description of the Prior Art
Cetain polymeric resins referred to as plastisols are fluid mixtures, ranging in viscosity from pourable liquids to heavy pastes, obtained by dispersing polymeric resin particles in nonvolatile, nonaqueous liquid plasticizers, i.e., materials which are compatible with the polymer or resin and increase its workability and flexibility but are not solvents for the resin or polymer under ordinary conditions of storage. When the plastisol has been formed into a desired shape, e.g., by molding or coating, it can be heated to coalesce the polymeric resin particles and the nonvolatile liquid constituent, thereby forming a homogeneous mass. Volatile diluents can be added to plastisol dispersions to modify their viscosity and to achieve desirable handling characteristics in coating or other forming operations. When the dispersion contains no more than 10% volatile diluent, it is still regarded as a plastisol; when the volatile diluent content exceeds 10%, the dispersion is defined as an "organosol", H. A. Sarvetnick, "Plastisols and Organosols", Van Nostrand Reinhold Company, New York (1972), page 201.
Theoretically, by appropriate choice of ingredients, any polymeric resin can be made into a plastisol. In practice, however, both the commercial use and the technical literature have focused almost exclusively on the use of polyvinyl chloride in forming plastisols, to the extent that "plastisol" is cross-referenced to "polyvinyl chloride" in Chemical Abstracts and in many textbooks plastisols are described as suspensions of polyvinyl chloride resin.
The pre-eminence of polyvinyl chloride in the practical and technical plastisol art results from the fact that many polymers with otherwise highly useful and desirable characteristics can be dispersed in suitable plasticizers only with great difficulty to give dispersions that have impractically high initial viscosities or very short storage life or both. It has now been found that plastisols and organosols of reduced initial viscosity and enhanced stability against room temperature gelation can be produced when polymers that contain ionogenic groups are first converted to their salts and then dispersed in plasticizers. Dispersions made in this way are amenable to a variety of forming techniques with all of the economic, ecological, health and safety advantages attendant on solvent-free operation. They can be made photosensitive by incorporation of a nonvolatile, photopolymerizable, ethylenically unsaturated compound as part of the plasticizer component of the dispersion, and used for the manufacture of relief and planographic printing plates, photoresists for the manufacture of printed circuits, and the like.
It is known from U.S. Pat. No. 3,309,330 to use terpolymers of vinyl chloride/acrylate/acrylic or methacrylic acid in aqueous dispersions that may contain a plasticizer as well as ammonium hydroxide. Such dispersions, however, are not polyelectrolyte resin plastisols or organosols. French Pat. No. 73.06503 teaches how to disperse multiple-phase polymers, including ionomers, in a mixture of polar and nonpolar plasticizers. Aqueous dispersions of polyelectrolyte resins in silver-halide-based photosensitive compositions and elements are disclosed in U.S. Pat. Nos. 1,981,102 (polyelectrolyte as hydrophilic binder for silver halide emulsion) and 3,811,897 (polyelectrolyte as viscosity-increasing additive in aqueous dispersions of hydrophilic colloids). U.S. Pat. No. 2,893,868 discloses photosensitive compositions and elements that comprise potopolymerizable, ethylenically unsaturated monomers in conjunction with polyelectrolyte resins and plasticizers dissolved in organic solvents. The compositions are solutions rather than dispersions.